Variable Displacement Compressor

ABSTRACT

This variable displacement compressor comprises: a housing; a piston; a drive shaft rotatably supported by the housing; a rotor that rotates in unison with the drive shaft; a swash plate that rotates in synchronism with the rotation of the rotor connected via a connecting means; a conversion mechanism that converts the rotation of the swash plate into a reciprocating motion of the piston; and a pressure control valve that is capable of controlling the internal pressure of a crank chamber. The variable displacement compressor is characterized in that: the connecting means directly or indirectly connects a first arm projecting from the rotor and a second arm projecting from the swash plate; and the drive shaft is eccentrically inserted into a through-hole that is perforated through the swash plate. With this configuration, it is possible to provide a variable displacement compressor in which the behavior of the swash plate can be stabilized with a simple structure and in which the swash plate can be inclined smoothly.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a variable displacement compressor, which is specifically used in an air-conditioning system for vehicles.

BACKGROUND ART OF THE INVENTION

A swash plate of a variable displacement compressor sometimes flaps with unstable behavior of the swash plate caused by reduced frictional force generated on a sliding surface between a circumferential surface of a drive shaft and a through-hole of the swash plate in which the drive shaft is inserted, when an inclination angle of the swash plate becomes small in a low load region to reduce a compressive load.

Patent document 1 discloses a technique of providing a relative-movement regulation means to stabilize the swash plate behavior to the drive shaft.

PRIOR ART DOCUMENTS Patent documents

Patent document 1: JP2002-364530-A

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

The technique to stabilize the swash plate behavior disclosed in Patent document 1 requires to provide a relative-movement regulation means, so that the introduction cost might be risen. Therefore an improved technique capable of suppressing such a cost rise is desired.

Accordingly, it could be helpful to provide a variable displacement compressor having a simple structure capable of stabilizing the swash plate behavior and inclining the swash plate smoothly.

Means for Solving the Problems

To achieve the above-described object, the present invention is a variable displacement compressor comprising a housing having compartments of a discharge chamber; a suction chamber; a crank chamber and a cylinder bore, a piston provided in the cylinder bore, a drive shaft rotatably supported by the housing, a rotor to rotate integrally with the drive shaft, a swash plate to rotate in synchronism with the rotor connected through a connecting means, a conversion mechanism that converts a rotation of the swash plate into a reciprocating motion of the piston, and a pressure control valve that is capable of controlling an internal pressure of the crank chamber according to a valve opening, wherein

when the valve opening is changed to change the internal pressure of the crank chamber, a discharge capacity for compressing and discharging a refrigerant sucked from the suction chamber into the cylinder bore is changed by changing a stroke of the piston through changing an inclination of the swash plate to the drive shaft while the swash plate slides on the drive shaft, characterized in that

the connecting means directly or indirectly connects a first arm projecting from the rotor and a second arm projecting from the swash plate,

the drive shaft being eccentrically inserted into a through-hole that is perforated through the swash plate.

Such a variable displacement compressor makes it possible that the side surface of the through-hole contacts one side of the circumferential surface of the drive shaft decentered in the through-hole, so that the swash plate behavior is prevented from being unstable by frictional force generated between the through-hole and the drive shaft when the swash plate moves in a direction to change its inclination. Such a structure can achieve a desired purpose without any cost increase.

It is preferable that the drive shaft is inserted eccentrically toward a positive rotation direction of the swash plate as viewed from a position corresponding to a top dead center position. With such a configuration, because the drive shaft is inserted into the through-hole eccentrically toward the positive rotation direction (compression process side) of the swash plate as viewed from the position corresponding to the top dead center position on the swash plate, the through-hole contacts the circumferential surface of the drive shaft at the positive rotation direction side (compression process side), so that the distance between the contact point and the point of compressive load is less than that of a case of contacting at diagonally opposite side (suction process side) to the contact point and therefore inclination motion blocking of the swash plate is prevented by frictional force.

It is preferable that the swash plate contacts the drive shaft in a compression process region at a side of the positive rotation direction from the position corresponding to the top dead center position while a gap is maintained between the swash plate and the drive shaft in a suction process region at another side of a negative rotation direction from the position corresponding to the top dead center position when the swash plate changes the inclination within a range of movement allowed by a gap between a connecting element which connects the first arm and the second arm and the first arm and another gap between the connecting element and the second arm. With such a configuration, the drive shaft in the through-hole cannot contact the side surface diagonally at two points, so that the inclination motion blocking of the swash plate is surely prevented.

EFFECT ACCORDING TO THE INVENTION

The present invention can provide a variable displacement compressor capable of making a smooth inclination motion with a simple structure.

BRIEF EXPLANATION OF THE DRAWINGS

FIG. 1 is a longitudinal section view showing a variable displacement compressor according to an embodiment of the present invention.

FIG. 2 shows the link arm in FIG. 1, where (a) is a top view and (b) is an arrow view from A direction shown in (a).

FIG. 3 is an arrow view showing a connected body of the drive shaft and rotor in FIG. 1.

FIG. 4 is an arrow view showing the swash plate in FIG. 1.

FIG. 5 shows the positional relation among rotor, drive shaft, link arm and swash plate in FIG. 1, where (a) is a plan view of the connected body of the rotor and drive shaft, (b) is a front view showing the link arm, and (c) is a plan view of the swash plate.

FIG. 6 is a partial enlarged schematic section view of an enlarged contact part between the swash plate and drive shaft in FIG. 5, where (a) shows a condition in which a swash plate surface having a through-hole is parallel to the drive shaft and (b) shows another condition in which the swash plate surface having the through-hole is oblique to the drive shaft.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

A variable displacement compressor according to the present invention can be explained visually with referring to virtual planes (plane U and plane V) as follows. The present invention is a variable displacement compressor comprising a housing having compartments of a discharge chamber; a suction chamber; a crank chamber and a cylinder bore, a piston provided in the cylinder bore, a drive shaft rotatably supported by the housing, a rotor that is fixed to the drive shaft to rotate integrally with the drive shaft, a swash plate that is attached as slidably contacting to the drive shaft through a through-hole in which the drive shaft is inserted to rotate in synchronism with the rotor connected through a connecting means to change an inclination from an axis line of the drive shaft, a conversion mechanism that converts a rotation of the swash plate into a reciprocating motion of the piston, and a pressure control valve that is capable of controlling an internal pressure of the crank chamber, wherein an opening of the control valve is adjusted to change the internal pressure of the crank chamber, a stroke of the piston is adjusted through changing the inclination of the swash plate, and a refrigerant sucked from the suction chamber into the cylinder bore is compressed and discharged to the discharge chamber, characterized in that

the connecting means comprises a first arm of the rotor provided with a guide surface, a second arm of the swash plate and a connecting element to connect the first arm to the second arm, and

the connecting means is configured such that a plane T offsets from a plane U, the plane T being parallel to the guide surface of the first arm and including the axis line of the drive shaft, the plane U being orthogonal to an annular plane of the swash plate and including a top dead center position of the swash plate and a center of both side surfaces of the through-hale slidably supporting a circumference of the drive shaft.

Such a variable displacement compressor makes it possible that the side surface of the through-hole contacts one side of the circumferential surface of the drive shaft decentered in the through-hole, so that the swash plate behavior is prevented from being unstable by frictional force generated between the through-hole and the drive shaft when the swash plate moves in a direction to change its inclination. Such a structure can achieve a desired purpose without any cost increase.

It is preferable that the plane T offsets toward a region of a compression process side from the plane U, if the swash plate is divided into the compression process side and a suction process side by the plane U that is orthogonal to the annular plane of the swash plate and includes the top dead center position of the swash plate and the center of both side surfaces of the through-hole slidably supporting the circumference of the drive shaft. Such a configuration of offsetting toward the region at the compression process side makes it possible that the through-hole contacts the circumferential surface of the drive shaft at the compression process side, so that the distance between the contact point and the point of compressive load is less than that of a case of contacting at diagonally opposite side (suction process side) to the contact point and therefore the inclination motion blocking of the swash plate is prevented by frictional force.

It is preferable that a hole diameter (horizontal width) of the through-hole of the swash plate is designed such that the circumferential surface of the drive shaft contacts only a compression process side surface of the through-hole. With such a configuration, the drive shaft in the through-hole cannot contact the side surface diagonally at two points, so that the inclination motion blocking of the swash plate is surely prevented.

Hereinafter, desirable examples of the variable displacement compressor will be explained with reference to the figures.

(1) Variable Displacement Compressor In FIG. 1, variable displacement compressor 100 as a clutchless compressor comprises cylinder block 101 having cylinder bores 101 a, front housing 102 provided at one end of cylinder block 101 and cylinder head 104 provided with valve plate 103 at the another end of cylinder block 101.

Swash plate 111 is provided around the middle of drive shaft 110 that crosses crank chamber 140 sectioned by cylinder block 101 and front housing 102. Swash plate 111 is provided with through-hole 111 a in which drive shaft 110 is inserted, and through hole 111 a is formed such that swash plate 111 is tiltable between the maximum inclination angle and the minimum inclination angle with axle K orthogonal to a plane that includes the top dead center and the bottom dead center of the swash plate and is orthogonal to the annular plane of swash plate 111. The said top dead center position of the swash plate means a position of piston 136 at the end of a compression process while the said bottom dead center position means a position of piston 136 at the end of a suction process. Swash plate 111 is connected to rotor 112 attached to drive shaft 110 through link mechanism 120 and the side surface of through-hole 111 a is slidingly supported by the circumferential surface of drive shaft 110 to make inclination angle variable.

Through-hole 111 a is provided with a minimum inclination regulation part brought into contact to drive shaft 110. It is preferable that the minimum inclination regulation part of through-hole 111 a is configured to have a swash plate inclination angle θ of 0° to less than 0.5° if the annular plane of swash plate 111 orthogonal to drive shaft 110 is assumed to have 0° of swash plate inclination angle θ.

Inclination-decreasing spring 114 as a compression coil spring biasing swash plate 111 down to the minimum inclination angle is provided between rotor 112 and swash plate 111, while inclination-increasing spring 115 as a compression coil spring biasing swash plate 111 up to predetermined inclination angle less than the maximum inclination angle is provided between swash plate 111 and spring support member 116. Because the biasing force of inclination-increasing spring 115 is designed as being greater than the biasing force of inclination-decreasing spring 114 at the minimum inclination angle, swash plate 111 is positioned to have a predetermined inclination angle so that the resultant force of the biasing force of inclination-decreasing spring 114 and the biasing force of inclination-increasing spring 115 is zero when drive shaft is not rotating.

One end of drive shaft 110 penetrates boss part 102 a projecting out of front housing 102 to extend outward, to be connected to a power transmission device not shown. Shaft seal device 130 is interposed between drive shaft 110 and boss part 102 a to block off the inside from the outside. Drive shaft 110 and rotor 112 are supported in a radial direction with bearings 131 and 132 and supported in a thrust direction with bearings 133 and thrust plate 134. A power is transmitted from an external drive source to the power transmission device to rotate drive shaft 110 in synchronism with the rotation of the power transmission device. The gap between thrust plate 134 and drive shaft 110 to contact thrust plate 134 is adjusted to a predetermined distance with adjusting screw 135.

Piston 136 is provided in cylinder bore 101 a and the outer periphery of swash plate 111 is housed in an inner space of an end of piston 136 projecting toward crank chamber 140. Swash plate 111 is designed to coordinate with piston 136 through pair of shoes 137. Thus piston 136 can reciprocate in cylinder bore 101 a as swash plate 111 rotates.

Cylinder head 104 is sectioned into suction chamber 141 at the center and discharge chamber 142 annularly surrounding radially outer part of suction chamber 141. Suction chamber 141 communicates with cylinder bore 101 a through communication hole 103 a and a suction valve (not shown) which are formed on valve plate 103. Discharge chamber 142 communicates with cylinder bore 101 a through discharge valve (not shown) and communication hole 103 b which is formed on valve plate 103.

Front housing 102, cylinder block 101, valve plate 103 and cylinder head 104 are fastened with through bolts 105 through a gasket not shown, to form a compressor housing.

In FIG. 1, a muffler is provided on a top of cylinder block 101, the muffler comprising lid member 106 and formation wall 101 b formed on the top of cylinder block 101 which are fastened by a bolt with an seal member not shown. Check valve 200 is provided in muffler space 143. Check valve 200 is provided at a connection part between communication path 144 and muffler space 143 and works in response to the pressure difference between communication path 144 (upstream) and muffler space 143 (downstream). For example, communication path 144 is blocked off when the pressure difference is less than a predetermined value and communication path 144 is opened when the pressure difference is greater than the predetermined value. Thus discharge chamber 142 is connected to a refrigerant cycle at the discharge side of an air-conditioning system via a discharge path comprising communication path 144, check valve 200, muffler space 143 and discharge port 106 a.

Cylinder head 104 is provided with suction port 104 a and communication path 104 b. Suction chamber 141 is connected to a refrigerant cycle at the suction side of the air-conditioning system via a suction path comprising communication path 104 b and suction port 104 a. The suction path linearly extends across a part of discharge chamber 142 from the radially outer part of cylinder head 104.

Cylinder head 104 is further provided with control valve 300. Control valve 300 controls an opening of communication path 145 communicating discharge chamber 142 and crank chamber 140, so that the amount of discharge gas introduced to crank chamber 140 is controlled. The refrigerant in crank chamber 140 flows to suction chamber 141 via communication path 101 c, space 146 and orifice 103 c formed on valve plate 103.

Therefore, the discharge capacity of variable displacement compressor 100 can be controlled variably by changing the pressure in crank chamber 140 with control valve 300 to change the swash plate inclination (namely, change the stroke of piston 136).

When the air conditioner is operated (namely, variable displacement compressor 100 is in operation), electricity applied to a solenoid embedded to control valve 300 is adjusted based on external signal to control the discharge capacity so that the pressure in suction chamber 141 is adjusted to a predetermined value. Control valve 300 is capable of desirably controlling the suction pressure depending on external environment.

When the air conditioner is not operated (namely, variable displacement compressor 100 is under suspension), electricity applied to the solenoid embedded to control valve 300 is turned off to force communication path 145 open to control the discharge capacity of variable displacement compressor at minimum.

(2) Link Mechanism

Drive shaft 110 is pressed to fix rotor 112 and pair of first arm 112 a is provided as projecting from rotor 112. In pair of first arms 112 a, one end 121 a of link arm 121 formed in an almost cylindrical shape is guided. First connecting pin 122 as a connection means is inserted into through-hole 112 b formed on first arm 112 a as well as through-hole 121 b formed on one end 121 a of link arm 121, so that link arm 121 can rotate around a shaft center of first connecting pin 122 as being guided by pair of first arms 112 a. First connecting pin 122 is pressed to be held to through-hole 121 b formed on link arm 121 while a small gap is formed between the circumference of first connecting pin 122 and through-hole 112 b formed on first arm 112 a.

Other end 121 c of link arm 121 is provided with a pair of arms projecting from one end 121 a formed in a cylindrical shape and guides second arm 111 b projecting from swash plate 111 thereinto. Second connecting pin 123 as a connection means is inserted into through-hole 121 d formed on other end 121 c of link arm 121 and through-hole 111 c formed on second arm 111 b, so that link arm 121 and swash plate 111 connected to link arm 121 can rotate relatively around a shaft center of second connecting pin 123. Second connecting pin 123 is pressed to be held to through-hole 111 c of second arm 111 b while a small gap is formed between the circumference of second connecting pin 123 and through-hole 121 d formed on link arm 121.

Link mechanism 120 consists of first arm 112 a, second arm 111 b, link arm 121, first connecting pin 122 and second connecting pin 123. Therefore, swash plate 111, which connects rotor 112 fixed to drive shaft 110 through link mechanism 120 and rotates by receiving rotation torque of rotor 112, can change its inclination along drive shaft 110.

(3) Connection State of Rotor, Link Arm and Swash Plate

FIG. 5 (a) shows a connected body of drive shaft 110 and rotor 112 viewed from swash plate 111. In the figure, symbol T implies plane T that includes an axis line of drive shaft 110 and is parallel to the inner surface (guide surface brought into contact with one end 121 a of the link arm) of first arm 112 a. Pair of first arms 112 a of rotor 112 are parallel to plane T and distance L1 between plane T and the guide surface of one end 121 a of the link arm of first arm 112 a 1 on the left is slightly greater than distance L2 between plane T and the guide surface of one end 121 a of the link arm of first arm 112 a 2 on the right. Namely, the guide surfaces of pair of first arms 112 a are not symmetric from plane T but the center of the guide surfaces of pair of first arms 112 a is offset from plane T toward the left in the figure by ΔL=(L1−L2)/2. ΔL is predetermined as considering the outer diameter of drive shaft 110 and the gap to the width of through-hole 111 a in plane V direction. The offset length of ΔL is more than 0.1 mm.

As shown in FIG. 5 (b), the center of pair of first arms 112 a corresponds to the center of link arm 121 and the guide surfaces of pair of arms 121 c to second arm 111 b are symmetrically provided.

FIG. 5 (c) shows swash plate 111 viewed from rotor 112. In FIG. 5 (c), symbol U implies plane U that is orthogonal to annular plane P of swash plate 111 and includes the top dead center position and the center of both side surfaces of through-hole 111 a while symbol V implies plane V that is orthogonal to annular plane P of swash plate 111 and includes axle K orthogonal to plane U. In plane U shown in the figure, the top side corresponds to the top dead center position of the swash plate while the bottom side corresponds to the bottom dead center position of the swash plate. The center of second arms 111 b corresponds to plane U. If the swash plate is sectioned into two regions by plane U in FIG. 5 (c), the left side is the suction process side and the right side is the compression process side.

Because plane U corresponds to the center of link arm 121 and the center of pair of first arms 112 a, plane T offsets by ΔL from the center of both side surfaces of through-hole 111 a of the swash plate toward the right direction (compression process side) in the figure.

As a result, drive shaft 110 is decentered toward the compression process side in through-hole 111 a, as shown in FIG. 6 (a).

Link arm 121 has each predetermined gap to first arm 112 a and second arm 111 b so that link arm 121 rotates around first connecting pin 122 and second connecting pin 123. As shown in FIG. 6 (b), the hole diameter (horizontal width in FIG. 5 (c)) of through-hole 111 a is designed such that the compression process side surface of through-hole 111 a contacts the circumferential surface of drive shaft 110 at contact part D without contacting at diagonally opposite part E to the contact part when link arm 121 and second arm 111 b incline left or right within the gap to allow a displacement.

Therefore, the reaction force of gas compression with piston 136 operated by variable displacement compressor 100 acts on swash plate 111 through piston 136, so that swash plate 111 slightly inclines by compressive load. In this way, the compression process side of through-hole 111 a contacts the circumferential surface of drive shaft 110 at only one side and therefore frictional force is generated between through-hole 111 a and drive shaft 110 when swash plate 111 inclines to increase the inclination angle. The behavior of swash plate 111 can be stabilized with the frictional force. In addition, marked blocking of the inclination motion of swash plate 111 is prevented because through-hole 111 a contacts drive shaft 110 at only one side without contacting even at diagonally opposite side.

Because the compression process side surface of through-hole 111 a contacts the circumferential surface of drive shaft 110 at contact part D so that the distance between the contact point and the point of compressive load is less than that of a case of contacting at diagonally opposite part E to the contact part, excessive frictional force is prevented from acting.

Although the above-described example shows that the first arm of the rotor offsets, it is possible that the link arm or the second arm of the swash plate offsets.

Although the above-described example shows the link mechanism as a connecting means, it is possible that the connecting means is a hinge mechanism as disclosed in Patent document 1.

Although the above-described example shows a case of a clutchless compressor, it is possible that the compressor is variable displacement compressor having an electromagnetic clutch, variable displacement compressor of wobble plate type, variable displacement compressor driven by a motor.

INDUSTRIAL APPLICATIONS OF THE INVENTION

The present invention is applicable to a variable displacement compressor for air-conditioning system for vehicles or the like.

EXPLANATION OF SYMBOLS

-   100: compressor -   101: cylinder block -   101 a: cylinder bore -   101 b: formation wall -   101 c: communication path -   102: front housing -   102 a: boss part -   103: valve plate -   103 a, 103 b: communication hole -   104: cylinder head -   104 a: suction port -   104 b: communication path -   105: through bolt -   106: lid member -   106 a: discharge port -   110: drive shaft -   111: swash plate -   111 a: through-hole -   111 b: second arm -   111 c: through-hole -   112: rotor -   112 a, 112 a 1, 112 a 2: first arm -   112 b: through-hole -   114: inclination-decreasing spring -   115: inclination-increasing spring -   116: spring support member -   120: link mechanism -   121: link arm -   121 a: One end of link arm -   121 b: through-hole -   121 c: other end of link arm -   121 d: through-hole -   122: first connecting pin -   123: second connecting pin -   130: shaft seal device -   131, 132, 133: bearing -   134: thrust plate -   135: adjusting screw -   136: piston -   137: shoe -   140: crank chamber -   141: suction chamber -   142: discharge chamber -   143: muffler space -   144, 145: communication path -   146: space -   200: check valve -   300: control valve -   D: contact part -   E: diagonally opposite part to contact part -   P, T, U, V: plane 

1. A variable displacement compressor comprising a housing having compartments of a discharge chamber; a suction chamber; a crank chamber and a cylinder bore, a piston provided in the cylinder bore, a drive shaft rotatably supported by the housing, a rotor to rotate integrally with the drive shaft, a swash plate to rotate in synchronism with the rotor connected through a connecting means, a conversion mechanism that converts a rotation of the swash plate into a reciprocating motion of the piston, and a pressure control valve that is capable of controlling an internal pressure of the crank chamber according to a valve opening, wherein when the valve opening is changed to change the internal pressure of the crank chamber, a discharge capacity for compressing and discharging a refrigerant sucked from the suction chamber into the cylinder bore is changed by changing a stroke of the piston through changing an inclination of the swash plate to the drive shaft while the swash plate slides on the drive shaft, characterized in that the connecting means directly or indirectly connects a first arm projecting from the rotor and a second arm projecting from the swash plate, the drive shaft being eccentrically inserted into a through-hole that is perforated through the swash plate.
 2. The variable displacement compressor according to claim 1, wherein the drive shaft is inserted eccentrically toward a positive rotation direction of the swash plate as viewed from a position corresponding to a top dead center position.
 3. The variable displacement compressor according to claim 2, wherein the swash plate contacts the drive shaft in a compression process region at a side of the positive rotation direction from the position corresponding to the top dead center position while a gap is maintained between the swash plate and the drive shaft in a suction process region at another side of a negative rotation direction from the position corresponding to the top dead center position when the swash plate changes the inclination within a range of movement allowed by a gap between a connecting element which connects the first arm and the second arm and the first arm and another gap between the connecting element and the second arm. 